This proposal consists of three studies concerned with the clinicopathological correlates and neuropsychological features of the Lewy body variant (LBV) of Alzheimer's disease (AD). In a retrospective study, neuropathological findings will be correlated with neuropsychological measures obtained during life. Measures of memory, attention, language, executive functions, and constructional abilities will be correlated with the number of Lewy bodies, synapses, plaques, tangles and neurons noted in various cortical and subcortical brain regions. In the first of two prospective studies, patients with clinically-defined probable AD or probable LBV will be compared on many of the neuropsychological measures used in the retrospective study. These comparisons will utilize quantitative and qualitative indices which have been shown to discriminate patients with AD from patients with progressive basal ganglia dementias. It is anticipated that patients with LBV will evidence many of the cognitive deficits associated with basal ganglia dementias. The second prospective study will involve the evaluation of the probable AD and probable LBV patients on three tests of implicit memory (pursuit rotor learning, weight biasing, prism adaptation) that involve the initiation and modification of central motor programs. Based upon previous findings, it is anticipated that the probable LBV patients, but not the probable AD patients, will be impaired on these tasks.